The next pope, Nicolas V, was a man who had raised himself from a humble station by his learning, ability, and good character. He was chiefly remarkable for his love of learning, and for the bounty which he spent on learned men. For learning had come to be regarded with very high honour, and those who were famous for it found themselves persons of great importance, who were welcome at the courts of princes, from the Emperor of the West down to the little dukes and lords of Italy. But we must not fancy that these learned men were all that they ought to have been. They were too commonly selfish and jealous, vain, greedy, quarrelsome, unthrifty; they flattered the great, however unworthy these might be; and in religion many of them were more like the old heathen Greeks than Christians.

      In the time of Nicolas, a terrible calamity fell on Christendom by the loss of Constantinople. The Turks, a barbarous and Mahometan people, had long been pressing on the Eastern empire, and swallowing up more and more of it. It was the fear of these advancing enemies that led the Greeks repeatedly to seek for union with the Latin Church, in the hope that they might thus get help from the West for the defence of what remained of their empire. But these reconciliations never lasted long, more especially as the Greeks did not gain that aid from their Western brethren for the sake of which they had yielded in matters of religion. One more attempt of this kind was made after the council of Florence; but it was vain, and in 1453 the Turks, under Sultan Mahomet II, became masters of Constantinople.

      A great number of learned Greeks, who were scattered by this conquest, found their way into the West, bringing with them their knowledge and many Greek manuscripts; and such scholars were gladly welcomed by Pope Nicolas and others. Not only were their books bought up, but the pope sent persons to search for manuscripts all over Greece, in order to rescue as much as possible from destruction by the barbarians. Nicolas founded the famous Vatican Library in the papal palace at Rome, and presented a vast number of manuscripts to it. For it was not until this very time that printing was invented, and formerly all books were written by hand, which is a slow and costly kind of work, as compared with printing. For in writing out books, the whole labour has to be done for every single copy; but when a printer has once set up his types, he can print any number of copies without any other trouble than that of inking the types and pressing them on the paper, by means of a machine, for each copy that is wanted. The art of printing was brought from Germany to Rome under Nicolas V, and he encouraged it, like everything else which was connected with learning.

      Nicolas also had a plan for rebuilding Rome in a very grand style, and began with the Church of St. Peter; which he intended to surround with palaces, gardens, terraces, libraries, and smaller churches. But he did not dlive to carry this work far.

      One effect of the new encouragement of learning was, that scholars began to inquire into the truth of some things which had long been allowed to pass without question. And thus in no long time the story of Constantine's donation and the false Decretals" were shown to be forged and worthless.

      The shock of the loss of Constantinople was felt all through Christendom, and Nicholas attempted to get up a crusade, but died before much came of it. When, however, the Turks, in the pride of victory, advanced further into Europe,and laid siege to Belgrade on the Danube, they were driven back with great loss by the skill of John Huniades, a general, and by the courage which John of Capistrano, a Franciscan friar, was able by his exhortations and his prayers to rouse in the hearts of the besieged.